Infrared Eyes Set For the Sky

On April 27, 2003, Boeing will launch the Space Infrared Telescope Facility (SIRTF) the fourth and final element in NASA’s family of Great Observatories.Credit: Ball Aerospace & Technologies Corp., 2003

Ed. note: The Space Infra-red Telescope Facility (SIRTF) was originally scheduled to be launched on April 17, then postponed to April 27, aboard a Delta II rocket from Cape Canaveral, Florida. It has now been postponed until at least mid-August. The delay gives engineers enough time to change one of the nine solid rocket motors attached to the Delta II rocket. The Mars Exploration Rovers are also scheduled to be launched on Delta II rockets on June 6 and June 25, and there was a decision that not enough time was available to remove and replace the rocket motor to support a SIRTF launch in advance of the Mars Exploration Rover-B launch window.

The Space Infrared Telescope Facility (SIRTF) was due to launch on Sunday, April 27. Like the Hubble Space Telescope, SIRTF has large mirrors that will provide unprecedented views of the universe. But while Hubble is mainly a visible-light telescope, SIRTF will detect infrared light. In other words, SIRTF will be hunting for heat.

That’s why SIRTF’s position in space will be very different from Hubble’s orbit around the Earth. SIRTF won’t circle the Earth at all – instead it will circle the sun. The observatory will tailgate the Earth, following a few million miles behind our planet in the same solar orbit.

This type of orbit will protect the telescope from the Earth’s infrared radiation. SIRTF also will carry a solar shield to protect itself from solar heat. The telescope will be kept in a liquid helium-insulated chamber in order to maintain a temperature of 5 degrees Kelvin (-268 C, or -451 F).

By keeping cool, SIRTF will be able to detect the infrared energy (heat) radiated by objects in space. The SIRTF observatory has two curved mirrors to gather this infrared light, and three instruments to interpret the data. The infrared array camera is a general-purpose camera for near-to-mid-infrared wavelengths. The infrared spectrograph works like a prism, spreading light out into its various wavelengths so astronomers can study the molecular composition of cosmic objects. The multi-band imaging photometer will provide images and limited spectroscopic data at far-infrared wavelengths.

Infrared light can penetrate the clouds of gas and dust that obscure our view of the universe. SIRTF should allow scientists to peer into regions of star formation, the centers of galaxies, and newly forming planetary systems. By studying dusty planet-forming discs around stars, SIRTF will aid in the search for Earth-like planets.

"We have two major ‘Legacy’ projects aimed at searching for dust disks associated with past or current planetary system formation around hundreds of stars," says Michael Werner, project scientist for SIRTF. "Data from these programs will become available eight months after launch."

Infrared light can also be used to study cooler objects in space, such as brown dwarfs, asteroids, and comets (above: mid-infrared view of Comet IRAS-Araki-Alcock).Image Credit: IRAS/Infrared Processing and Analysis Center

Infrared light can also be used to study cooler objects in space, such as brown dwarfs, asteroids, and comets. Comets are thought to have played a role in the development of life on Earth, seeding our planet with organic molecules and water. SIRTF also will be able to search interstellar space for carbon-rich organic molecules. The observatory may ultimately help us understand the processes by which life formed.

"A major area for SIRTF contributions to astrobiology will be in the spectroscopic study of carbon-bearing molecules and solids in the interstellar medium and in circumstellar shells," says Werner.

SIRTF was first proposed in 1979, but formal approval to start the project was not granted until 1996. Advances in technology over the years helped improve the overall design of the observatory. The original launch date was December 2001, but this was pushed back due to problems with computer hardware and software.

Werner says this delay was not unexpected, since the SIRTF project is extremely complex and involves a good deal of new technology. He says that all of the problems have now been solved, and the SIRTF team has built a lot of redundancy into the telescope to try to minimize any new problems that might arise.

"We are aware of the risks associated with SIRTF and discuss them constantly," says Werner, who plans to be at Cape Canaveral when SIRTF blasts off into space on its Delta 2 rocket. "We will all breathe a huge sigh of relief when we get our first telemetry back an hour after launch, reporting that we have the sun on the solar panels and that everything is behaving nominally."

What’s Next

SIRTF will get a new name after it is launched. NASA held a contest to re-name the telescope, and over 7,000 people submitted suggestions. The spacecraft’s new name will be revealed at a press conference four months after launch. The first SIRTF images will be available at that time, as well.

SIRTF is the last of the "Great Observatories" that NASA first proposed in the 1970s. Each observatory examines the heavens in a different electromagnetic spectrum. Because they are space borne telescopes, orbiting above the distorting atmosphere of the Earth, they are able to gain unprecedented views of the universe. The most famous is the Hubble Space Telescope, the visible light telescope, and it is expected to operate until 2010. The Compton Observatory, launched in 1991, examined gamma rays until its mission ended in 1999. The Chandra Observatory, launched in 1999, examines X-rays and is scheduled to operate through 2004.

SIRTF has a 2.5-year mission, although it could be extended to 5 years. Because SIRTF will lag a little further behind the Earth as time goes by, after 5 years SIRTF will be about 50 million miles away.